Viewing a thread - Can someone explain to me hydraulic fitting sizes....

WiReading through this whole thread shows the confusion that exists mainly due to different industries slang terms.

Not to beat the dead horse, but some of this will be reorganized repeats.

Lets start with sizing.

The "dash" sizing is what you are referring to and is what many fittings and hoses go by. It came from the US military after the Aeronautical and Navy agreed on a standard. The standard was and still is called "AN". You won't find AN fittings on your farm though, they are aluminum fittings, generally anodized and used with braided stainless or kevlar hose as well as forms of hard tubing. It is used extensively in aviation and is the choice for almost every motorsport due to its serviceability. Assembling AN hoses is a lengthier process than whipping up a hydraulic hose though.

The AN standard used a 37* Flare that created the seal. Dash sizing is easy to figure out, its simply in 1/16ths. I actually prefer the dash system anyways. Much easier to hear dash 4 or Dash 12 over the than it is to try and distinguish between 1/4 and 3/4. I assume this could partially be why the military chose it.

The fittings we all have on our equipment use the same threads, the same sizing and the same 37* flare as their AN counterparts but are built much heavier. (AN fittings and hose typically aren't rated much over 300psi whereas JIC is rated up to 5,000psi )

JIC stands for Joint Industry Council. Essentially, awhile back, everybody got together and agreed on that style fitting for use in many things, in an effort to make things more "standard".


Below are the most common Hydraulic Fitting styles you will find on a North American machine.

NPT: National Pipe Thread. Known by many names, but the key features are a tapered thread that relys on thread distortion to form the seal. On the newer "improved NPT" fittings the "thread sealer" is acting more as a lube than anything to encourage the threads to deform to each other without error. These fittings generally have a 30* internal taper as well right at the edge when using true Hydraulic fittings. Many people will use black pipe or galvanized pipe instead which can lead to poor results, or expensive repairs. Hydraulic pipe thread pieces are made out of steel. NPT's upside is that it is very simple, very cheap and very common. The downside is that it is not very serviceable. Often times the fittings are rigid making removal and installation difficult. In addition the fittings wear out quickly and loose their ability to seal. They take much more torque to achieve a good seal and take much more time to install due to the need to physically distort the threads.

37* JIC: Probably the most common right alongside NPT. As explained earlier, utilizes male/female 37* flares to create the seal. You will generally find that most hard steel lines have JIC threads, some older ones have NPT though. JIC's advantage's include easier installation due to them generally having a swivel at both ends and being able to run the fitting on the majority of the way by hand. JIC is not very expensive compared to other models but can be considerably higher than NPT. The downside to JIC is that it is very sensitive to overtightening, which many people fail to observe. Most are so used to cranking on NPT fittings that they feel the need to put their weight into a JIC fitting. Proper torques on these fittings are very very low. So low they make special wrenches so you don't over do it. Overtightening will slowly ruin the flare and the fitting becomes useless. There are inserts available that act as a sealing washer though.

45* SAE: This fitting is similar to the 37* in many ways. However it is rarely used in hydraulic systems. Generally it is reserved for Fuel, Oil, and Air systems on vehicles. Semis are full of these fittings. Most are Brass and running under lower pressures. Don't need to worry about it much for hydraulics as you will rarely run into one if ever.

STORB: Straight Thread O-Ring Boss. Sometimes just called O-ring boss, sometimes SAE O-ring, other times O-ring port fittings, and a number of other combonations. The main thing to remember are the key aspects, SAE straight threads, O ring seal on threads. These fittings rely on an O-ring seated in a boss above the threads to seal things up. They are generally used as adapters for going into hydraulic rams, motors, distribution blocks, etc etc. Its not too often that they are crimped directly onto the hose, but there are some cases where this is true. The advantages to STORB are that it is serviceable. O-ring kits are available with the proper o-rings. Another big advantage is that 90* fittings can be oriented in the direction that they are needed if the proper fitting is chosen. Installation is quick, but again these generally are installed to adapt a valve block to JIC or ORFS fitting on the hose.

ORFS: O-Ring Face Seal. These fittins are also called O-Ring Seal, when referring to the STORB fittings O-Ring Boss is generally used. Seal is on the face, Boss is on the threads. Easy to remember. These fittings also have straight threads, but utilize an o-ring mounted in the face of the male fittings to do the sealing. The Females are almost all swivel and have a flat face inside them that mates up to the o-ring to seal. These are becoming more and more popular. Construction equipment is almost exclusively using this style along with split flange. Advantages to this style are its durability. Generally rated for double what JIC can handle, these fittings seal very well. They are serviceable too. Kits are available with the proper O-rings. They install very nicely and are more forgiving if over tightened. Disadvantages to this style are prices and availability. I stock all of them in our shop, but most of the dealers and parts stores around here that do hoses do not stock a full line except for the Parker Store and NAPA. They are the most money out of any of the fittings, mostly due to supply and demand though. These are by far my favorite style of fitting to use if possible.

Code 61/62: These are generally called "Split Flange" fittings because they incorporate two flanges that clamp the fitting into place. Most often these are found on pumps and some large hydraulic rams. Think of the ORFS face and magnify it. These fittings essentially use the same concept just use two flanges to mount them instead of a threaded nut. Advantages are that they can be put in very tight spaces, easy to mount to pumps and such, serviceable, easy to install as well. They are relatively cheap but again, supply demand plays a role which keeps the price up.

Inverted Male Flare: This is one you will only find in power steering and hydraulic brake systems generally. It uses a pipe with an internal flare and a nut that presses on the out edges of the flare to seat it into the port it is going into.



Hopefully that clears up the styles of fittings somewhat. If you need charts on how to measure them to make sure you get the right one there are plenty all over the internet to download, otherwise let me know and Ill post one.


As important as the fittings is the hose. There are many to choose from but making sure you have the proper hose is key. For most farmers purposes 2 wire does most of it. Higher pressure components though will used 4 wire hose and such. Then there are other special hoses too that are sometimes used. Its important to note that as you change hose types, different fittings become incompatible. So if you are mad at the hose guy because he has the fitting you need but he says it wont work with the hose you need, that is why.

Same applies for crimping ends onto old hoses. Most places won't do it, and its in your best insterest not to. If you have to get going and the proper stuff is not available you can try it, but its just temporary. The major issue is incompatibility between hoses and ends. If you have eaton hose, you use eaton ends, etc. The crimp dimensions are very precise, over crimping or under crimping can case more headaches than it is worth. In addition, the hose has already been compromised by a hole in it somewhere which has exposed the internal steel to the elements and started deteriorating it. Its always cheapest to make a new hose in the long run.

Clean hoses count too. Best to use a scallop blade or hydraulic hose saw for cutting the hose as it will leave less debris behind. The only way to truely get the hose cleaned out though is to use a foam gun which shoots a foam pellet through the hose to scrape everything out of it. Not many shops have these. They run $1,000+. The CAT shops do have them though.

Don't forget to orientate your ends correctly too. Know a lot of guys who just crimp two 90's on and say its fine because the hose is long enough they can "twist/flex" it enough to get it one. In reality what you are doing is putting the hose in a pre-loaded state versus relaxed, which leads to premature failure.

Good name brands of Hoses and Fittings are Eaton Weatherhead, Parker, and Gates.

If you can make all your own hoses, its nice. Maybe do them for the neighborhood? Usually what we end up doing. I stock every Eaton Weatherhead fitting style in their "U" series and 100+' of H245 Hose in the following sizes, 04,06,08,10,12 & 16. It ends up being around 300 or so fittings. Also stock 50-100' of 6 different sizes of Kevlar wrap as well as the Oetiker Clamps for clamping it on cleanly. Overall, this inventory ended up costing between 15,000-20,000. Our supplier has a good deal that as long as you buy from them, you get to keep a crimper, the needed dies and as many storage cabinets as needed for a small refundable deposit. I acquired them over the past couple years. Many of them are not on any of our machines, but maybe someday will be. There is nothing I hate more than to have someone come here for a hose and I have to say that we dont have the right ends. In addition, the amount of time and money that setup saves us year round is immense. Its very nice for customizing/building equipment as well.

After doing a search on GJ for oring face seal fittings (orfs), the results kept sending me to this thread.

I have a two stage import hydraulic (manual) pump with an output male elbow fitting that appears to be an orfs with a metric 6.0 x 1.8 o-ring size called out in the parts diagram... thread type unknown.

With it came an import cylinder with welded on male nipples also appearing to be orfs, but with a metric 7.5 x 1.8 o-ring size called out in the parts diagram... thread type unknown.

Both the pump and the cylinder shipped with threaded caps on the ports, and the caps are different on the inside (thread depth to the end of the cap) but appear to interchange between ports, suggesting that the threads may be the same, even if the sealing surface o-rings are not the same.

The easiest solution would be to order the OEM hose assembly for the pump and cylinder, but it is an import, and the wait time for such a hose assembly was quoted as AT LEAST 4 months, with no guarantees that the part would ever arrive.

I thought, no problem, I can always get a hydraulic hose locally. Not so. First, the 10,000 psi rating appears to be a rarity. And even where that is surmountable, once stepping outside the realm of JIC, it is back in the land of rarity it seems.

This rarity appears to include transitional fittings to get from orfs to JIC.

It doesn't help that both the pump and the cylinder are terminated with male threads, which means I need females on the hose. Swiveling females (that need not swivel once tightened).

I am currently dog paddling out of my depth, but am hoping that continued research will bring me to a better understanding of how incompatible fittings from China, where most things are made that I can afford, are interfaced with locally obtainable hydraulic hoses and fittings.

Any direction and advice is appreciated.

After doing a search on GJ for oring face seal fittings (orfs), the results kept sending me to this thread.

I have a two stage import hydraulic (manual) pump with an output male elbow fitting that appears to be an orfs with a metric 6.0 x 1.8 o-ring size called out in the parts diagram... thread type unknown.

With it came an import cylinder with welded on male nipples also appearing to be orfs, but with a metric 7.5 x 1.8 o-ring size called out in the parts diagram... thread type unknown.

Both the pump and the cylinder shipped with threaded caps on the ports, and the caps are different on the inside (thread depth to the end of the cap) but appear to interchange between ports, suggesting that the threads may be the same, even if the sealing surface o-rings are not the same.

The easiest solution would be to order the OEM hose assembly for the pump and cylinder, but it is an import, and the wait time for such a hose assembly was quoted as AT LEAST 4 months, with no guarantees that the part would ever arrive.

I thought, no problem, I can always get a hydraulic hose locally. Not so. First, the 10,000 psi rating appears to be a rarity. And even where that is surmountable, once stepping outside the realm of JIC, it is back in the land of rarity it seems.

This rarity appears to include transitional fittings to get from orfs to JIC.

It doesn't help that both the pump and the cylinder are terminated with male threads, which means I need females on the hose. Swiveling females (that need not swivel once tightened).

I am currently dog paddling out of my depth, but am hoping that continued research will bring me to a better understanding of how incompatible fittings from China, where most things are made that I can afford, are interfaced with locally obtainable hydraulic hoses and fittings.

Any direction and advice is appreciated.

Fittings that meet the O-ring face standards don't have metric o-rings.

Buying a fitting to get from standard O-ring face (which you don't have) to JIC (which isn't rated to 10,000 PSI in any size) won't help you.

Your fittings are weird just to prevent people from screwing random crap on there and killing yourself, and your family or estate suing the manufacturer of the thing you misused.
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First thing you need to figure out is what you actually have for fittings. Get a set of metric and standard thread pitch gauges, and a caliper. If you can figure out what you have, you may be able to find somebody who makes jack hose (10k psi hose in small diameters is commonly called jack hose) with the goofy ends you need. Otherwise you're stuck waiting for the goofy Chinese hose to match the goofy Chinese fittings your stuff has.

First thing you need to figure out is what you actually have for fittings. Get a set of metric and standard thread pitch gauges, and a caliper.

@bigfunwmu

Here are the measurements that you suggested that I take. Thank you for your interest and any insight you can provide.

Using three thread pitch gauges...
A. Metric
B. Fractional
C. "SAE"

I found the 1.5 mm per thread pattern on the metric thread pitch gauge appeared to match the best.

Albeit, while the thread crown/crest points matched (aided by a flashlight back lighting the gauge and the threads), and the gauge nested fully into the valley/root of the threads, the thread angle appears more U shaped rather than V shaped, which allowed the 1.5 mm gauge to shift axially a little bit back and forth between thread flanks more than I am used to seeing.

Several attempts were made to find a better fit from the entire fan of choices in all three thread gauges, with 16 TPI being a distant second best on the fractional/SAE gauges, yet the crest cadence was off, evidenced after about 5 threads.

Thus, the closest actual match where the crests aligned for the entire length of threads was the 1.5 mm per thread gauge.

The threads appear to be straight... in other words, I could not detect any type of pipe like taper to the root diameter that grew in size as the threads advanced toward the body of the fitting. I clumsily attempted to verify this observation with the dial caliper, as described below.

Using a 6" dial caliper (wish I had better/smaller), reset to zero, measuring in thousandths, and converted to millimeters...

1. The overall diameter, crest to crest was 0.551" / 14 mm

2. The root diameter, root to root, was 0.500" / 12.7 mm at the entrance thread, and again was 0.500" / 12.7 mm at the terminating thread.

Based on your earlier response above, I will no longer call these fittings O-ring face seal, but they do have an O-ring, which appears to seat and seal in the flat face of the fitting, within the machined perimeter ring ledge that helps keep the O-ring in place.

Both the pump fitting and the cylinder fitting have raised machined ledges that appear to assist in locating the face mounted sealing O-ring. However, while the raised machined ledge on the pump fitting is around the perimeter, capturing the O-ring by surrounding the outside diameter of the O-ring, by distinct contrast, the raised machine ledge on the cylinder fittings is within the inside diameter of the O-ring, with no raised ledge on the outside diameter such as what the pump has. Likewise, in continued contrast, the pump fitting has no raised ledge capturing the inside diameter of the O-ring.

I have observed photos of ORSF fittings that have two machined raised ledges to keep the O-ring in place that capture both the inside AND the outside diameters of the O-ring, rather than just one OR the other, like the fittings I have.

I measured the metal dimensions that the O ring seats within and seals on the pump fitting.

3. Inner diameter of the fluid orifice within the fitting, surrounded by the O-ring: 0.197" / 5 mm

4. Maximum diameter of the O-ring seat, excluding the machined perimeter ring ledge that contains the O-ring: 0.370" / 9.4 mm

5. Face width of the outer perimeter raised machined ring ledge that contains the O-ring: 0.065" / 1.65 mm (approximated, as the outer walls of this ledge taper into the first thread)

The foregoing measurements apply to the single outlet fitting on the 2 stage manual pump.

The following measurements apply to the single acting hydraulic cylinder fittings (there are two fittings, comprised of welded on male nipples, where one nipple appears to be for a force gauge, and the other nipple is to receive the pressurized oil from the pump).

The metal dimensions that the O-ring seats within and seals on the cylinder fittings are as follows:

6. The overall diameter, crest to crest was 0.550" / 14 mm

7. The root diameter, root to root, was 0.500" / 12.7 mm at the entrance thread, and again was 0.500" at the terminating thread.

8. Inner diameter of the fluid orifice within the fitting, that is also the inner diameter of the machined raised ledge that retains and centers the O-ring: 0.197" / 5 mm

9. Maximum diameter of the O-ring seat, including the machined interior ring ledge within the inside diameter of the O-ring: 0.455" / 11.56 mm (This is approximated, as the outside edges taper off into the first thread)

10. Face width of the inner raised machined ledge defining the fluid orifice, surrounded by the O-ring that this ledge helps locate: 0.055" / 1.4 mm

Summary:

The pump male fitting and the cylinder male fitting have the same 1.5 mm thread pitch.

Both also have seats for O-rings on their fitting faces.

However, the location of the raised machined ledges that retain the O-ring in position differ between the pump fitting and the cylinder fittings. The pump fitting has a machined raised ledge on the perimeter of the face, outside of the O-ring, with no ledge or protrusion at the orifice. On the other hand, the cylinder fitting has a machined raised ledge that defines the orifice, on the inside of the O-ring, without any perimeter raised ledge on the outside of the O-ring.

Another difference is that the male nipple fittings on the cylinder have fewer threads, 5 on one fitting and 6 on the other, while the pump male fitting has 10 threads. The cylinder fittings with fewer threads appear to have yet another O-ring land at the base of the threads, where an O-ring is rolled over the threads and seats like a hula hoop surrounding the threadless root diameter of the nipple. The fewer threads on the cylinder fittings appear to be intentional, so as to accommodate this additional O-ring at the neck of the nipple, just below the threads.

Finally, the metric hex wrench size to open the threaded caps is 17 mm. The interiors of the caps between the pump and the cylinder appear to differ from each other in terms of number of threads, but they both have the same 1.5 mm thread pitch.